It would work as an underbelt for certain.
A girthbelt in canon and in real life is a very specific thing. It's actually an equestrian belt for horses and is made from several mohair fiber cords. In canon it is a symbol of being (or having been) a Journeyman Protector, like a police or sheriff badge or star.
You can actually get an equestrian mohair girthbelt for about $15.00 shipped through www.horseloverz.com
That belt there would be just fine but, it would not be a girthbelt.